Early Vegetative Growth Stage Research Articles

Variability of Root and Shoot Traits under PEG-Induced Drought Stress at an Early Vegetative Growth Stage of Soybean

Variability of Root and Shoot Traits under PEG-Induced Drought Stress at an Early Vegetative Growth Stage of Soybean

Unrevalling phenotypic diversity of root system architecture in ancient wheat species versus modern wheat cultivars

Understanding the phenotypic variability in root system architecture and root-shoot relationships across different growth stages of wheat is of utmost importance for the improvement of genotypes with enhanced nutrient uptake and resource-use efficiency. This study focused on identifying variations and relationships in the root and shoot characteristics of seven modern cultivars and twelve ancient wheat accessions of different species, including T. monococcum, T. turanicum, T. polonicum, T. mirabile, T. durum, and T. aestivum, during the early vegetative growth and stem elongation stages. The results demonstrated significant phenotypic variation among the genotypes for shoot traits, root biomass, rooting depth, R/S ratio, and seminal and nodal root numbers. When considering both growth stages, the dry land-adapted cultivar ‘Taner’ and ancient wheat species, such as T. turanicum (2) and T. monococcum (1) accessions, exhibited deeper roots, which can enhance access to water in drought-prone areas. Furthermore, it was observed that modern wheat cultivars and T. turanicum accessions exhibited increased root biomass, suggesting a higher allocation of resources towards root growth, which could potentially enhance nutrient uptake. Conversely, T. monococcum accessions and T. mirabile revealed lower root biomass compared to other ancient species and modern cultivars. Additionally, the unrooted cluster analysis based on root biomass, rooting depth, and root to shoot ratio at both growth stages indicated a distinct separation of T. monococcum accessions and T. mirabile from other genotypes. Overall, these findings underscore the importance of phenotypic diversity in root traits for crop improvement and adaptation to varying environments. Identifying genotypes with desirable root characteristics can enhance nutrient and water uptake efficiencies, leading to increased crop productivity and sustainability.

Assessing the influence of furrow width on growth and yield of soybean in ridge-furrow relay intercropping system with flax

Soybean flax ridge-furrow relay intercropping system is a new method of intercropping system to distress excessive vegetative growth of soybean during the rainy season. However, the effects of furrow width for flax on growth and yield of soybean in ridge-furrow relay intercropping system remain unclear. In this study, we investigated that the effects of three treatments (FS1: 10 cm furrow width, FS2: 20 cm furrow width, FS3: 30 cm furrow width) on growth and yield of soybean and clarified informative principal data for soybean flax ridge-furrow relay intercropping system. In a three-year field experiment, soybean was grown in ridges and flax was grown in furrows. At the early vegetative growth stage of soybean, environmental conditions such as water, light, and temperature, in ridge-furrow relay intercropping system, decreased significantly by interspecific competition in comparison with sole cropping system. The differences in environmental conditions between sole cropped and intercropped treatments increased in accordance with increasing width of flax furrow. Especially, soil moisture content, photosynthetically active radiation (PAR), and temperature in FS3 were 39.9%, 29.6%, 4.4 ℃ lower than those of SS, respectively, on average of 3 years. At the reproductive growth stage, expanding furrow width for flax decreased the number of abscised leaves, plant height, leaf area index (LAI), and specific leaf area (SLA) of intercropped soybean, while increased PAR penetration within the canopy and stem diameter. At 130 DAS, average numbers of abscised leaves in FS2 and FS3 were 4 and 5 lower than that of SS, respectively. Plant height of soybean was 0.3 m lower than that of SS in both FS2 and FS3. In LAI, the value of sole cropped soybean varied between 6.8 and 7.2, but it in FS2 and FS3 varied between 3.4 and 4.3. Particularly, LAI in FS2 ranged from 4.1 to 4.3. Average stem diameter of soybean was 0.3 cm higher than that of SS in both FS2 and FS3. PAR penetration at 30 cm below soybean canopy in FS1, FS2, and FS3 was 111.2, 122.5, 133.0% of that in SS, respectively. These led to a higher crop growth rate (CGR), reproductive growth rate (RGR), and grain distribution in intercropped soybean, as compared to sole cropped soybean. Among three treatments, FS2 exhibited the maximum CGR, RGR, and grain distribution. Also, FS2 achieved maximum soybean yield of 4.9 t ha−1 (averaged by 2020, 2021, and 2022) and maximum land equivalent ratio (LER) of 2.1 (averaged by 2020, 2021, and 2022). No significant difference in LER was observed between FS2 and FS3; however, soybean yield in FS2 was significantly higher compared to FS3 across each year. Our results suggest that by selecting the appropriate furrow width, we can constrain the excessive vegetative growth more effectively and increase the yield of soybean under ridge-furrow relay intercropping system with flax.

Genome-Wide Association Studies of Seven Root Traits in Soybean (Glycine max L.) Landraces.

Soybean [Glycine max (L.) Merr.], an important oilseed crop, is a low-cost source of protein and oil. In Southeast Asia and Africa, soybeans are widely cultivated for use as traditional food and feed and industrial purposes. Given the ongoing changes in global climate, developing crops that are resistant to climatic extremes and produce viable yields under predicted climatic conditions will be essential in the coming decades. To develop such crops, it will be necessary to gain a thorough understanding of the genetic basis of agronomic and plant root traits. As plant roots generally lie beneath the soil surface, detailed observations and phenotyping throughout plant development present several challenges, and thus the associated traits have tended to be ignored in genomics studies. In this study, we phenotyped 357 soybean landraces at the early vegetative (V2) growth stages and used a 180 K single-nucleotide polymorphism (SNP) soybean array in a genome-wide association study (GWAS) conducted to determine the phenotypic relationships among root traits, elucidate the genetic bases, and identify significant SNPs associated with root trait-controlling genomic regions/loci. A total of 112 significant SNP loci/regions were detected for seven root traits, and we identified 55 putative candidate genes considered to be the most promising. Our findings in this study indicate that a combined approach based on SNP array and GWAS analyses can be applied to unravel the genetic basis of complex root traits in soybean, and may provide an alternative high-resolution marker strategy to traditional bi-parental mapping. In addition, the identified SNPs, candidate genes, and diverse variations in the root traits of soybean landraces will serve as a valuable basis for further application in genetic studies and the breeding of climate-resilient soybeans characterized by improved root traits.

Evaluating Chemical Suppression Treatments to Alter the Red: Far-Red Ratio in Perennial Groundcovers for Maize Production

Perennial groundcover (PGC) has great potential to deliver ecosystem service benefits and control weeds in annual row crop systems. Inadequately suppressed PGC, however, acts as an early-season weed, causing a shade avoidance response (SAR) in maize (Zea mays L.) before the critical period for weed control (CPWC) even with resource abundance. The SAR results from a low red to far-red light shift, impairing early season plant growth and decreasing yield. A field study was conducted in Ames, IA, USA to assess application timing of groundcover suppression chemicals on maize growth and development. Two suppression chemical treatments (paraquat or paraquat + glufosinate) were each applied to “Midnight” Kentucky bluegrass (Poa pratensis L.) PGC once on the day of maize planting (DOP) or consecutive maize stages from VE to V6 in a randomized complete block design with unsuppressed groundcover control. Response variables included maize plant height, maize phenological development stage, reflected red:far-red (R:FR) ratio above the PGC canopy, early vegetative and final maize plant density, maize yield and components, and weed communities. Suppression increased reflected R:FR ratio from the groundcover immediately after application. Where suppression was applied at later stages, low R:FR ratio during early vegetative growth stages triggered a maize SAR and maize plant etiolation. Final maize plant height and yield were greater in PGC suppressed at earlier maize stages, although no suppression treatment provided adequate suppression duration. Paraquat + glufosinate more effectively suppressed groundcover overall and limited groundcover competition, producing 8% greater maize grain yield than paraquat alone in year 1, and 13% greater stover and 8% greater total aboveground biomass (TAB) in year 2. Weather conditions influenced chemical suppression efficacy in year 2, emphasizing the importance of identifying reliable chemical suppression to support grain yield from the day of maize planting.

Indian Mustard and Buckwheat as Trap Plants of Diamondback Moth (Plutella xylostella L.) in Cabbage Cultivation

Diamondback moth (Plutella xylostella) is an important pest of crucifer crops. It greatly reduced both yield and crop quality on cabbage (Brassica oleracea var. capitata). The field study was conducted to evaluate the efficacy of two trap plants: Indian mustard (Brassica juncea), and Buckwheat (Fagopyrum esculentum) from November 2018 to March 2019 in Chitwan, Nepal. Diamondback moths’ population were similar in trap plants but was significantly lower as compared to the control plot. Diamondback moth larvae population was lower during early vegetative growth stages whereas trapping efficacy of trap crops were gradually reduced with the development of maturity in trap plants. The lowest damage of wrapper leaves were obtained in Indian mustard deployed trap plant followed by buckwheat trap plant and control respectively; however, the yield was similar in all treatments. In addition, natural enemies were observed higher in traps crops deployed plots compared to the control plots. Therefore, trap plants can be used as an alternative sustainable pest management tool to manage diamondback moth as well as increase the abundance of natural enemies.

Maize Canopy and Leaf Chlorophyll Content Assessment from Leaf Spectral Reflectance: Estimation and Uncertainty Analysis across Growth Stages and Vertical Distribution

Accurate estimation of the canopy chlorophyll content (CCC) plays a key role in quantitative remote sensing. Maize (Zea mays L.) is a high-stalk crop with a large leaf area and deep canopy. It has a non-uniform vertical distribution of the leaf chlorophyll content (LCC), which limits remote sensing of CCC. Therefore, it is crucial to understand the vertical heterogeneity of LCC and leaf reflectance spectra to improve the accuracy of CCC monitoring. In this study, CCC, LCC, and leaf spectral reflectance were measured during two consecutive field growing seasons under five nitrogen treatments. The vertical LCC profile showed an asymmetric ‘bell-shaped’ curve structure and was affected by nitrogen application. The leaf reflectance also varied greatly between spatio–temporal conditions, which could indicate the influence of vertical heterogeneity. In the early growth stage, the spectral differences between leaf positions were mainly concentrated in the red-edge (RE) and near-infrared (NIR) regions, whereas differences were concentrated in the visible region during the mid-late filling stage. LCC had a strong linear correlation with vegetation indices (VIs), such as the modified red-edge ratio (mRER, R2 = 0.87), but the VI–chlorophyll models showed significant inversion errors throughout the growth season, especially at the early vegetative growth stage and the late filling stage (rRMSE values ranged from 36% to 87.4%). The vertical distribution of LCC had a strong correlation with the total chlorophyll in canopy, and sensitive leaf positions were identified with a multiple stepwise regression (MSR) model. The LCC of leaf positions L6 in the vegetative stage (R2-adj = 0.9) and L11 + L14 in the reproductive stage (R2-adj = 0.93) could be used to evaluate the canopy chlorophyll status (L12 represents the ear leaf). With a strong relationship between leaf spectral reflectance and LCC, CCC can be estimated directly by leaf spectral reflectance (mRER, rRMSE = 8.97%). Therefore, the spatio–temporal variations of LCC and leaf spectral reflectance were analyzed, and a higher accuracy CCC estimation approach that can avoid the effects of the leaf area was proposed.

Spatial distribution and sequential sampling plan for Diceraeus melacanthus (Hemiptera: Pentatomidae) in maize at the vegetative stage

Diceraeus melacanthus has become a key pest of maize in Brazil, primarily during the early vegetative growth stages. This study examined the spatial distribution of D. melacanthus in maize and developed a sequential sampling plan for monitoring the pest in maize at the vegetative stage. The samples were collected from six fields of 1250 m2 each in the second crop seasons of 2012 and 2013. The sampling unit consisted of five randomly chosen plants per plot, which were visually examined for D. melacanthus on a weekly basis, totaling 250 plants evaluated per field on each sampling date. To construct the sampling plan, an economic threshold of 0.8 stink bugs per sample unit (five plants) was adopted. According to the indices of dispersion and by fitting the frequency data to mathematical distributions, the spatial distribution of D. melacanthus in maize is aggregated. From the obtained data, two decision lines were generated, one of which, S1 = 3.5683 + 0.5702 N, recommends taking control action, whereas the other, S0 = −3.5683 + 0.5702 N, suggests that no control action is needed. The sequential sampling plan indicated an expected maximum number of 26 sampling units (∼130 plants) to determine whether to control the pest with prefixed precision level of 95%. This sampling plan may help the decision-making for the control of D. melacanthus in maize, contributing for a sustainable management of this herbivore to increase farmers’ profit.

High-Throughput Root Imaging Analysis Reveals Wide Variation in Root Morphology of Wild Adzuki bean (Vigna angularis) Accessions.

Root system architecture and morphological diversification in wild accessions are important for crop improvement and productivity in adzuki beans. In this study, via analysis using 2-dimensional (2D) root imaging and WinRHIZO Pro software, we described the root traits of 61 adzuki bean accessions in their early vegetative growth stage. These accessions were chosen for study because they are used in Korea’s crop improvement programs; however, their root traits have not been sufficiently investigated. Analysis of variance revealed a significant difference between the accessions of all measured root traits. Distribution analysis demonstrated that most of the root traits followed normal distribution. The accessions showed up to a 17-fold increase in the values in contrasting accessions for the root traits. For total root length (TRL), the values ranged from 82.43 to 1435 cm, and for surface area (SA), they ranged from 12.30 to 208.39 cm2. The values for average diameter (AD) ranged from 0.23 to 0.56 mm. Significant differences were observed for other traits. Overall, the results showed that the accession IT 305544 had the highest TRL, SA, and number of tips (NT), whereas IT 262477 and IT 262492 showed the lowest values for TRL, SA, and AD. Principal component analysis showed an 89% variance for PC1 and PC2. K-mean clustering explained 77.4% of the variance in the data and grouped the accessions into three clusters. All six root traits had greater coefficients of variation (≥15%) among the tested accessions. Furthermore, to determine which root traits best distinguished different accessions, the correlation within our set of accessions provided trait-based ranking depending on their contribution. The identified accessions may be advantageous for the development of new crossing combinations to improve root features in adzuki beans during the early growth stage. The root traits assessed in this study could be attributes for future adzuki bean crop selection and improvement.

Predicting the Chlorophyll Content of Maize over Phenotyping as a Proxy for Crop Health in Smallholder Farming Systems

Smallholder farmers depend on healthy and productive crop yields to sustain their socio-economic status and ensure livelihood security. Advances in South African precision agriculture in the form of unmanned aerial vehicles (UAVs) provide spatially explicit near-real-time information that can be used to assess crop dynamics and inform smallholder farmers. The use of UAVs with remote-sensing techniques allows for the acquisition of high spatial resolution data at various spatio-temporal planes, which is particularly useful at the scale of fields and farms. Specifically, crop chlorophyll content is assessed as it is one of the best known and reliable indicators of crop health, due to its biophysical pigment and biochemical processes that indicate plant productivity. In this regard, the study evaluated the utility of multispectral UAV imagery using the random forest machine learning algorithm to estimate the chlorophyll content of maize through the various growth stages. The results showed that the near-infrared and red-edge wavelength bands and vegetation indices derived from these wavelengths were essential for estimating chlorophyll content during the phenotyping of maize. Furthermore, the random forest model optimally estimated the chlorophyll content of maize over the various phenological stages. Particularly, maize chlorophyll was best predicted during the early reproductive, late vegetative, and early vegetative growth stages to RMSE accuracies of 40.4 µmol/m−2, 39 µmol/m−2, and 61.6 µmol/m−2, respectively. The least accurate chlorophyll content results were predicted during the mid-reproductive and late reproductive growth stages to RMSE accuracies of 66.6 µmol/m−2 and 69.6 µmol/m−2, respectively, as a consequence of a hailstorm. A resultant chlorophyll variation map of the maize growth stages captured the spatial heterogeneity of chlorophyll within the maize field. Therefore, the study’s findings demonstrate that the use of remotely sensed UAV imagery with a robust machine algorithm is a critical tool to support the decision-making and management in smallholder farms.

EFFECT OF PEG-INDUCED DROUGHT STRESS ON MUNGBEAN PLANTS REVEALED RESISTANT VARIETIES BASED ON LEAF WILTING INDEX AND BIOCHEMICAL MOLECULES

At the early vegetative growth stage, mungbean are mostly affected by drought, and it is also one of the most promising stages that can be used to screen for drought stress tolerance traits in multiple varieties. Therefore, this study utilized polyethylene glycol (PEG-6000) to induce drought stress towards selection of drought tolerance mungbean varieties in their early vegetative growth stage using both hydroponics and soil based systems. In this study, leaf wilting index and responses of biochemical molecules were used as the basic factors to determine the effect of PEG-induced drought stress among the mungbean varieties. Prior to the imposition of drought stress, germination potentials of the varieties were evaluated and all had germination = 60%. Except for Tvr29 and Tvr44, hydroponic system revealed that = 80% of the varieties had = 1 of their leaves significantly (P = 0.05) wilted. The highest LWI were recorded for Tvr49 and Tvr79. Re-evaluation of Tvr29, Tvr44, Tvr49 and Tvr79 using soil, shows that Tvr29 and TVr44 resisted drought stress. The hydrogen peroxide, superoxide radical and malondialdehyde contents decreased in TVr29 and Tvr44, and increased in Tvr49 and Tvr79 in comparison to the control. Tvr29 and Tvr44 had high proline content than Tvr49 and Tvr79. Based on LWI and biochemical molecules, this study revealed that Tvr29 and Tvr44 should be utilized where water deficit is a challenge to mungbean globally.

Varying drought stress induces morpho-physiological changes in cowpea (Vigna unguiculata (L.) genotypes inoculated with Bradyrhizobium japonicum

Increased environmental fluctuations because of climate change have been forecasted in many agricultural regions to increase the frequency, intensity, and duration of drought episodes, which threaten the sustainability of future crop production. Although cowpeas are drought-tolerant, recent evidence shows that soil water stress in the early stages of vegetative growth significantly impairs crop growth and development, with detrimental impacts on yields. Diversity in cowpeas has been extensively genotyped and sequenced to enhance drought stress tolerance based on genetic diversity, population structure, and phylogenetic relationships. Hence, this study was conducted to evaluate whether cowpea genotypes with contrasting drought-tolerant status respond differently to varying moisture stress under a controlled environment. Three cowpea genotypes, including Arkansas Blackeye #1 (ARB), Top Pick Cream (TPC), and 17–111 were subjected to 28 days of three volumetric water content (VWC) treatments, which comprised of 0.270, 0.203, and 0.135 m3m−3, identified respectively as well-watered (WW), intermediate drought (ID), and drought-stressed (DS) conditions. After 28 days of VWC treatment (DAT), it was observed that the seedlings of all cowpea genotypes survived, showing different characteristics of the DS effect. The results showed that plant height (PH), leaf area (LA) and number (LN), fresh (FM) and total dry mass (TDM) of cowpea genotypes were significantly decreased under DS compared to WW and ID. Furthermore, cowpea genotypes subjected to DS showed significant reductions in their rate of photosynthesis (Pn) at 14 DAT when compared to 28 DAT. Thus, suggesting cowpeas tend to adapt to DS with time. Similar results were obtained for stomatal conductance (gs), intercellular CO2 concentration (Ci), and transpiration rate (E). However, the water use efficiency (WUE) increases linearly under DS. DS also resulted in the decline of chlorophyll fluorescence parameters except non-photochemical quenching (qN) which increased with decreasing VWC treatments. Overall, the ARB was observed to have significantly highest Pn, gs, E, Ci, LA, PH, Jmax, and Vcmax at DS, ID, and WW when compared to TPC and 17–111 cowpea genotypes, indicating its tolerance to DS. Cowpea breeders may use the contrasting drought-tolerant genotypes and identified morpho-physiological features to develop new genotypes that could tolerate DS during the vegetative stage in future climates.

Season and Nitrogen Fertilization Effects on Yield and Physicochemical Attributes of Strawberry under Subtropical Climate Conditions

Strawberry (Fragaria ×ananassa Duch.) yields in winter production regions are greatly affected by early-season nitrogen (N) fertilization, especially when pre-plant N is not applied. In Florida, United States, applying N at high rates during the early season is a common fertilization practice, but little is known about its impact on fruit quality. The objective of this study was to examine season and early-season N fertilization effects on yield and physicochemical attributes of ‘Florida Radiance’ strawberry grown under subtropical climate conditions. Field experiments were conducted in west-central Florida over two growing seasons. Plants were treated with three N rates (1.12, 1.68, and 2.24 kg/ha/d) over 21 days during the early vegetative growth stage. Thereafter, all plants were treated with the same N rate of 1.12 kg/ha/d until the end of the season. Increasing the early-season N rate increased marketable yield by 15% to 18%, but it had no significant effect on any fruit quality attributes. Contrarily, marketable yield was similar in both seasons, whereas fruit quality showed remarkable seasonal variations. In the season with higher solar radiation and lower temperature, RH, and rainfall during the fruit development period, berries were redder with increased anthocyanin accumulation but had lower pH, acidity, and soluble solids. These results suggest that season has a greater effect on fruit quality than early-season N fertilization, which is complex to dissect because of the interaction between fruit quality attributes and environmental conditions. The use of high N rates during the early season appears to be an effective strategy to improve the profitability of winter strawberry production. Importantly, this fertilization technique has a minimal risk of compromising fruit quality or fertilizer N use efficiency.

Wild emmer introgression alters root-to-shoot growth dynamics in durum wheat in response to water stress

Water deficit during the early vegetative growth stages of wheat (Triticum) can limit shoot growth and ultimately impact grain productivity. Introducing diversity in wheat cultivars to enhance the range of phenotypic responses to water limitations during vegetative growth can provide potential avenues for mitigating subsequent yield losses. We tested this hypothesis in an elite durum wheat background by introducing a series of introgressions from a wild emmer (Triticum turgidum ssp. dicoccoides) wheat. Wild emmer populations harbor rich phenotypic diversity for drought-adaptive traits. To determine the effect of these introgressions on vegetative growth under water-limited conditions, we used image-based phenotyping to catalog divergent growth responses to water stress ranging from high plasticity to high stability. One of the introgression lines exhibited a significant shift in root-to-shoot ratio in response to water stress. We characterized this shift by combining genetic analysis and root transcriptome profiling to identify candidate genes (including a root-specific kinase) that may be linked to the root-to-shoot carbon reallocation under water stress. Our results highlight the potential of introducing functional diversity into elite durum wheat for enhancing the range of water stress adaptation.

Assessing Physiological and Genetic Evidence for Evolution of Shared Weedy Rice Traits at the Vegetative Growth Stage

Weedy rice (Oryza spp.) has successfully adapted to invasion of cultivated rice (O. sativa L.) fields by being a strong competitor from the early vegetative growth stages to crop harvest. While seed shattering and seed dormancy have been shown to contribute to competitiveness at the reproductive stage, much less is known about the traits that could contribute to weedy rice adaptation at the vegetative stage. We examined several growth and physiological traits in five different weedy rice lineages with different ancestral origins, and found that no single vegetative phenotype characterizes all weedy rice. Divergence in growth and physiological traits between weedy rice groups and their putative cultivated ancestors has been limited, suggesting that altered vegetative traits have not been a common path to weed adaptation. There is a lack of convergence in patterns of gene expression in two independent weedy rice lineages, suggesting that there are few shared genetic mechanisms in the evolution of vegetative traits. We conclude that it must not be assumed that all weedy rice groups necessarily have altered vegetative growth or physiological mechanisms compared to their ancestors, that facilitate their invasion of crop fields.

Root-based characterization of intergeneric hybrids with Triticum and Aegilops species in early vegetative and stem elongation growth stages

Cultivated and wild species of wheat are valuable breeding resources used for the development of new cultivars with superior root traits suited to drought and non-stressed conditions. The present study aimed to determine genotypes with superior root traits and phenotypic variability among intergeneric hybrids with Triticum and Aegilops species in the early vegetative (Z11) and stem elongation (Z31) growth stages. Results indicated that phenotypic variability in rooting depth was 3.2- and 3.4-fold among the genotypes in Z11 and Z31, and it was as great as 20- and 23.8-fold for root biomass, respectively. Hierarchical clustering among 35 genotypes for root traits in both growth stages identified four major clusters, grouping the six deep-rooted genotypes in cluster 2 and three genotypes with high root biomass in cluster 1. In both growth stages, significant associations were found among the root traits. Also, the relationship was stronger between the root and shoot biomass in Z11 (r2=0.83) than in Z31 (r2=0.44). As an overall assessment, the suggested genotypes with superior root characteristics such as deep roots and/or high root biomass sustained in both growth stages might be used for the development of new cultivars.

Low soil phosphorus availability triggers maize growth stage specific rhizosphere processes leading to mineralization of organic P

In this study, we examine the rhizosphere processes influencing organic P (Po) utilization in soil with low inorganic P (Pi) availability and how they change with plant development. Interactions between plants and the rhizosphere microbial community triggered by P deficiency may provide insights into the role of P availability on degradation of soil organic matter (SOM). Maize (Zea mays) plants were grown in low P containing soil. Soil pH, potential acid phosphatase activities, soil C and P pools, microbial biomass C and P, microbial community structure, and plant P content were analyzed at different vegetative growth stages (VGS). At early VGS, the plants were P deficient which correlated with greater rhizosphere potential acid phosphatase activity, degradation of SOM and a reduction in the Po pool. At late VGS, the plants appeared to recover which correlated with a decrease in Meh (III) extractable P, an increase in microbial biomass C and P, change in microbial community structure, and greater total P (TP) in the plant biomass. The mineralization of organic C and Po are coupled in low P soil where N is not limited. The overall findings from this study advance our understanding of the coupled biogeochemical rhizosphere processes controlling P cycling at different plant growth stages and notably the importance of Po to the overall P needs of plants in soil with low Pi availability.

Earthworm contributions to soil nitrogen supply in corn-soybean agroecosystems in Quebec, Canada

Accurately quantifying the soil nitrogen (N) supply in crop fields is essential for enabling environmentally sustainable and economically profitable crop production. It requires using field-based methods to account for the contribution of soil biota, including earthworms, to N mineralization in temperate agroecosystems. The direct contribution of earthworms to the soil N cycle is the N they release throughout their life and after death, and it can be estimated using the secondary production method. This study was conducted in 2014 and 2015 in two adjacent fields with annual corn-soybean rotation in Ste-Anne-de-Bellevue, Quebec, Canada. The cumulative biomass of Aporrectodea spp. in two no-till corn-soybean agroecosystems was determined, and the direct N flux from these earthworms was estimated during the corn and soybean phases of the rotation. Secondary production was estimated by sampling earthworms biweekly during April–June and September–November and inferring the change in earthworm biomass between sampling dates using a size frequency calculation. The N flux was calculated as the sum of the N released through excretion, during periods when earthworms were active, and from mortality. The secondary production of the Aporrectodea population was estimated to be 8–43 g ash-free dry weight m–2 year–1, and the N flux was 22–105 kg N ha–1 year–1. The N flux was higher at the early vegetative growth stage, which is a period of high N demand for corn. These findings suggest that refining the N fertilization recommendation by accounting for soil N supplied by earthworms could potentially reduce fertilizer costs and environmental N losses.

Effect of different durations of moderate ozone exposure on secondary metabolites of Brassica campestris L. ssp. chinensis

ABSTRACT Tropospheric ozone is an important ambient atmospheric pollutant component in urban areas. Determining plant reactions to ozone in plant growth and biochemical quality contents plays an important role in understanding plant metabolism. This study aimed to provide an understanding of the effect of ozone on early vegetative growth stage Pak-Choi (Brassica campestris L. ssp. chinensis). An experiment was conducted within an airtight bio-chamber for six consecutive days under 60 ppb ozone concentration. Different exposure duration conditions were 0 h/day, 1 h/day, and 4 h/day. The results showed no reaction of plant growth, but ozone exposure led to significant impacts in biochemical quality. The content of photopigments was not significantly impacted at 1 h/day, but significantly increased at the 4 h/day exposure condition. There was a significant decrease in the total glucosinolate (GLS) and total aliphatic GLS after the 4 h/day exposure condition; however, 4-Methylthiobutyl-GLS, total indole, and aromatic GLS were significantly increased. It appears that biochemical systems are more sensitive than the systems controlling plant growth, and this needs to be taken into account when implementing urban production sites for vegetables.

Soft computing-based approach on prediction promising pistachio seedling base on leaf characteristics

Fruit trees breeding is a time-consuming process. It can save time and cost in a fruit breeding program if promising genotypes can be predicted at the early stages of vegetative growth. In the current study, Artificial neural networks analysis (ANNs) has been used to predict promising pistachio with large nuts and green kernels based on leaves characteristics at the juvenile stage. Eight morphological traits related to leaf properties of 95 pistachio genotypes in a segregating population were used to predict the number of dry nuts per ounce (Npo) and kernel color classification using radial basis function (RBF). The results of Npo modeling using RBF showed that the root mean square errors (RMSE) for the training and testing phases are 0.28 and 0.37, respectively. R2 of 99% prediction also indicated that Npo could be estimated from leaf characteristics. Besides, the results of kernel color classification based on leaf characteristics also showed that the RBF is able to distinguish the pistachio kernel color with 98.95 per cent accuracy. The results also showed that the terminal leaflet apex (TLA) is the most critical leaf characteristic in the detection of Npo and kernel color. Based on Npo and green kernel the PIS-41, PIS-46, PIS-57, PIS-62, and PIS-67 genotypes were promising and can be used future breeding program.